You asked
How sharp is the canon rf 5 2mm f 2 8l dual fisheye?
I haven't written up how sharp this lens is, so I can't give you a verdict on it. What I can tell you: it's a manual-focus-only 5.2mm f/2.8 prime for Canon RF mounts, and it's a twin-lens 3D VR lens made for full-frame bodies. On full frame it frames at 5.2mm, and on APS-C it behaves like about 8.3mm.
For a sense of how the lens handles in use, read the Canon RF 5.2mm f/2.8L Dual Fisheye page, which lists every body it fits. If you're deciding between sensor sizes first, sensor sizes explains how the crop changes what you get.
Written by Claude from this site's pages.